Film insert moulding technology has become established for the production of plastics parts in the injection moulding process. It involves first two- or three-dimensionally prefabricating the frontal surface of a part from a coated film and then filling or insert moulding it with a polymer melt from the reverse side.
It is often desirable that the front side has sufficient protection from chemical and mechanical effects. This is often achieved in the prior art by an appropriate coating or paint system on the surface. In order to avoid wet coating of the finished three-dimensional parts, it is advantageous that such a paint or coating system should already have been applied to the film which then runs through all the further forming steps with the film and is then ultimately cured, for example by UV exposure.
This gives rise to a very specific profile of properties for coated films which suit this technology. In the prior art, the term “formable hardcoating” has become established for this product class, meaning a film coating which is at first sufficiently blocking-resistant, but then can be thermally formed as desired together with the substrate and at the end receives the properties of a protective layer through UV curing.
Such a combination of properties, in the sense of blocking resistance and thermoplastic characteristics of the primary coating, together with the great latent potential for UV crosslinking, is difficult to implement.
Most of the approaches to a solution for this objective in the prior art comprise the use of macromonomers which are prepared principally by dual-cure processes, as described inter alia in Beck, Erich (BASF), Scratch resistant UV coatings for automotive applications, Pitture e Vernici, European Coatings (2006), 82(9), 10-19; Beck, Erich, Into the third dimension: three ways to apply UV coating technology to 3D-automotive objects, European Coatings Journal (2006), (4), 32, 34, 36, 38-39; Petzoldt, Joachim; Coloma, Fermin (BMS), New three-dimensionally formable hardcoat films, JOT, Journal fuer Oberflaechentechnik (2010), 50(9), 40-42; EP 2113527 Al; Petzoldt et al., Development of new generation hardcoated films for complex 3D-shaped FIM applications, RadTech Asia 2011, Conference Proceedings.
The insert moulding of these film products with, for example, polycarbonate melt (film insert moulding) results in the desired plastics parts.
Furthermore, principally for reasons of design, there exists a great need to be able to provide those plastics parts which find wide use in automobiles, in all other modes of transport, in electrical and electronic devices, in domestic appliances, in sanitary articles, in the furniture industry and in the jewellery industry with a metal layer such as, more particularly, a chromium layer. In this way, the advantages of the plastic, for example free shaping and low weight, are combined with the high-quality appearance of metal surfaces. Also of interest are partially metallized components, with part of the area left without metallization for emblems, scales or viewing windows. These areas have to meet the high demands on media resistance that are placed on coated plastics parts, for example with respect to skin creams, cockpit care products, solvents, and a certain scratch resistance. Uncoated thermoplastics, for example the acrylonitrile-butadiene-styrene copolymer (ABS) which is of very good suitability for the desired galvanization, are inadequate in relation to solvent resistance and scratch resistance, measured, for example, by customary demands for the automobile interior or higher-quality electrical and electronic devices.
The process of galvanization of plastics is described in detail in the literature, for example in B. D. Rathmann in Chemie in unserer Zeit 15 (6) 1981, page 201 ff. and D. Bernd in Kunststoffgalvanisierung in der Praxis [Plastics Galvanization in Practice], Crash Course at Kunststoffinstitut Lüdenscheid 2012, Conference Book. It is known in the prior art that the plastics of best suitability for such a galvanization include ABS copolymers. Polycarbonate/ABS coextrusion films, as described, for example, in WO 2012/120007 A1, are in need of improvement in two aspects: As a result of the coextrusion process, ABS layers of this kind cannot be thinner than 15-20 μm. At thicknesses of 20 μm upwards, these layers are not as transparent as would be desired in some applications. Moreover, ABS layers of this kind do not meet the demands indicated on solvent resistance, and therefore cannot be regarded as a protective layer for plastics parts, as is actually expected from a layer which forms the surface of the film or of a moulded component thereof.
For these reasons, there is a great need in industry for coated films having a coating which firstly has adequate blocking resistance for further processing after the application and first drying operation, and secondly has a certain scratch resistance and solvent resistance after curing by means of UV light, for example, and is additionally also galvanizable. The fulfilment of such a profile of properties with the combination of properties mentioned constitutes a particular challenge to the person skilled in the art.